Method of introducing air to burners of reversing type furnaces



May 8, 1956 J. L. HARTNEY 4 METHOD OF INTRODUCING AIR TO BURNERS OF REVERSING TYPE FURNACES Original Filed March 9, 1950 5 Sheets-Sheet 1 I FROM FURNACE ZJ Z1 f? if a I 122 him-- 1- 2/ f7 56 it? ilf! wmaaw m J. L. HARTNEY May s, 1956 METHOD OF INTRODUCING AIR TO BURNEIRS OF REVERSING TYPE FURNACES Original Filed March 9, 1950 5 Sheets-Sheet 3 S u i g "I" lllll hweiuaxr JAM/5 L. Ha en/[K 4a A044 D m=h on INTnoDUCING AIR RliiVERslNG-TYPE FURNACES ETnoD James L. Hartney, Chicagtg lllt, assignor taunted States- Steel Corporation, a corporation of New Jersey 1 Original application 1Mar ch 9, .1950, Serial No. 148,619,' now Patent No. 2,669,419,"dated November24, 195 3. Dividedand this application May 27,1953, Serial No.

Claims. Cl, 263-52 ing such air to either burner or set of burners in a revers ing type furnace, and avoiding overheating of the equipment during changeovers.

A further object is to provide. a. method of directing fiowof compressed 'air fromua heating device to either burner or set of burners'ina reversing type furnace and automatically maintaining continuousflow-of such fluid through the heating device duringchangeovers and there-' by preventing 'overheating of the heating device 1 A further object is to provide improved methods of atomizing liquid fuel in open hearth furnace burners in which preheated compressed air is used as the atomizing fluid, thereby enhancing furnace efficiency over that obtained with steam as atomizing fluid.

In accomplishingthese and other objects of the invention,-l have-provided improved details of structure,

a preferred form of which is shown in the accompanying drawings, in which:

Figure 1 is aschematic view of a reversing type furnace equipped for introducing preheatedair to the burners in accordance with the method of the preserit-;invention;

Figurel is'a-top plan view with parts broken away T BURNERS 0F a 2,744,744 Patented May 8, {21956 ice" a' 'by -pass valve for: said regulator, The furnace,

'bu'rr'iers, air compressor, receiving tank, and pressure regulator may be of any standard construction; hence no more detailed 'description'is deemed necessary. The preferred construction of heat exchangerjis described more fully hereinafter.

, maintained'betweeii 75 and 125 pounds per square inch, although none of thesevalues are necessarilyf'critical, as

long as they are maintained constant or nearly" so.

' u A line 21 extends from the heat exchanger and branches into'linesf22 and 23 which extend respectively to burners 12 and- 13. iThese} lines contain normally closed, pneurnatically-. operated fdiaphragm' typevalves'24and 25 respectively*f0r controlling flow of air't'o the. burners. Inasmuch as thes'e valves may be of anystaudard construction and .per s'e are not part'oftheipiesent invention, no morejdetailed.description is deemed necessary. When the "furnace is fired-.froin either burner, the appropriate valve is opened and directs'air to that burner.

The apparatus comprises a by-pass line 26' which discharges from pipe 21 into the atmosphere and which contains a' valve 27. This valve is of the normally open,

' pneumatically operated 'double diaphragnr type and is 'more fully describedzhereinafte'r.

nace. Such circulation isjn'eeded to prevent overheating of a preferred construction of heat, exchanger used in t g the apparatus shown in Figure l; 7

Figures 3 and 4 are vertical sectional views of the heat exchanger taken respectively on lines III-'III andIVVIV of Figure 2;

Figure 5 isan by-pass valve used in the apparatus shown in Figure '1;

and

enlarged vertical sectional View oft he heatexchanger showingthe wall construction;

of the heat exchanger, since the temperature of air emergin'gfr'om'the heat exchanger can be fairly close to themaxirrium temperature which the heat exchanger can withstand. Also if the heat exchanger is overheated, there issubsequent'diificulty in. adjusting the air temperature to the desired constant; I

The valve operating mechanisznincl'udes a control air line 28 which is connected with line 17 and thus receives compressed airfromtank 16. Line 28 preferably conboth maybeof anystandard construction; Line 28 ex-' tends to a 'four-way control valve 31, to which'arealso connected to an exhaust line 32 and two lines '33 and V 34 thatextend to ,valves'24. and 25 respectively for op- Figure 7 .is-an exploded sectional viewof the operat- There isshown at 14 an air compressor which directs compressed air throughua line 15 to a receiving tank 16. From thetank-the air passes via a line 17 into a heat exchanger 18, where theair is heated to a fairly high temperature'which is maintained constant or nearly so. Line 17 preferably has 'a-pressure regulator19 and crating these- .valves, Valve 31 has setting to connect line 28 with either line-33 or 34 and at the same time connect the-other of these lines with exhaust line 32. Triasmuch as valves. having such setting are ,known and- P 356 are not part of'the present invention, nor more'detailed description is deemed necessary. Wheueverthe' control valv e i'admi'ts air to line 33 or. 34, -valve 24 or ZSo ensan'd-air flows through that valve fromtheheat exchanger "toone of the burners. Air lines 35 and-36extend from air lines 33 and 34 respectively to the by-pass valve 27. Whenever control valve 31 is. actuatedto relieve the'pressure on the. diaphragm of 'either of the normally closed valves 24 or 25 and thus-close this valve, it also relieves the pressure that The apparatus corny and thus prevents overheating of the heat exchanger.

The bypass valve remains open until pressure is applied to the diaphragm of the other valve 24 or 25 to open this valve. At the same time pressure is applied automatically to the by-pass valve via line 35 or 36 and thus this valve closes, and circulation is resumed to one of the burners.

A preferred construction of heat exchanger 18 is shown in detail in Figures 2 to 5. The heat exchanger comprises an enclosure whose walls are formed of a heat insulation lining 37 supported by longitudinally extending channelshaped casing members 38. Pairs of end plates 39 are interposed between successive tiers of insulating material and casings (Figure A spacer 40 and a horizontal bafile 41 are interposed between each pair of end plates 39. The battles are supported cantilever fashion from the end plates and thus are free to expand and contract. The baffles. extend'alternately from opposite sides into the interior of the heat exchanger as best shown in Figure 3 anddefine a sinuous course for circulating waste products. of combustion from the furnace from which the heat is derived.

A fan 42 draws a portion of the products of combustion from furnace into the lower portion of heat exchanger 18 through an inlet 43. These productsof combustion pass through the heat exchanger in the course defined by baffies 41 and are expelled at the top through an outlet 44 into a stack 45 (Figure 1). The portion of such products which pass through the heat exchanger is governed by a damper 46 preferably located in outlet 44.

The compressed air is maintained at a substantially constant temperature, which may be controlled .by regulating damper 46. Line 21 contains a temperature indi flow indicating eating device 47 and line 17 contains a devices 48. Damper 46 is regulated in accordance with readings on these indicating devices to maintain a flow of products of combustion through the heat exchanger sufiicient to heat the air to just the desired temperature. Although the damper may be regulated manually, the apparatus preferably includes metering controls, connected to the temperature and flow indicating devices 47 and 48 but not shown, for regulating the damper automatically. Inasmuch as such controls are known and do not per se form a part of the present invention, no

more detailed description is deemed necessary.

The heat exchanger has a pair of manifolds 49 and 50, each of which is divided by partitions 51 and into a plurality of superposed compartments (Figure 4). The compartments on opposite manifolds are connected by U- shaped tubes 52, which extend between bafiles 41 into the path of circulation of the products of combustion. Un-

heated compressed air is introduced from line 17 to the top chamber of manifold 49, whence it passes through tubes 52 to the top chamber of manifold 50. Such air then returns to the second chamber of manifold 49 via the next set of tubes 52. Air circulation between the manifolds continues through the entire height of the manifolds and the heated air finally discharges from the bottom chamber of manifold 49 into line 21, be directed to either set of burners as already explained.

Figures 6 and 7 show a preferred construction of bypass valve 27. Said valve includes the usual body, stem and closures, which are not shown in detail, since they may be of any standard construction. The operating mechanism for this valve includes a pair of superposed flexible diaphragms 53 and 54 housed within the usual pressure chamber 55. A spring 56 normally urges the diaphragms to a retracted position against the back wall of the chamber and normally maintains the valve open. Air may be admitted to the space behind diaphragm 53 to close the valve, or air may be admitted to the space between the two diaphragms also to close the valve. The first of these spaces is connected to line 36 by a connection from which it may 57 in the back wall of the chamber. The second of these spaces is connected to line 35 by a connection 58 situ-.

ated in a spacer ring 59 between'the two diaphragms. The first space preferably has fillers 60 and the second fillers 61 to separate the diaphragms slightly from the end Wall and from each other when either is retracted. Thus it is seen that the by-pass valve is closed Whenever air is admitted behind either diaphragm on closing of either valve 24 or 25.

From the foregoing description, it is seen that I have provided an efficient method for introducing preheated compressed air to either burner'or set of burners in a reversing type furnace. The air is continuously heated by heat derived from waste products of combustion and circulation of air is automatically maintained at all times including during changeover periods. ThusI have provided a method in which there. is no likelihood ofparts being overheated by failure to maintain air circulation.

The present application is a division of my copending application Serial No. 148,619, filed March 9, 1950, (now Patent No. 2,660,419 issued November 24, 1953) which in turn was a continuation-in-part of my application Serial No. 47,034, filed August 31, 1948 (now Patent No. 2,587,153 issued February 26, 1952). A While I have shown and described only a single embodiment of the invention, it is apparent that modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended claims.

I claim:

1. A method of introducing air alternately to an opposed pair of burners in a reversing type furnace comprising preheating compressed air, directing such air to the burner through which the furnace is being fired while stopping flow of air to the other burner, and maintaining air flow through the preheating equipment during changeovers to the other burner while flow of air to both burners is stopped.

2. A method of introducing air alternately to an opposed pair of burners in a reversing type furnace com prising preheating compressed air with heat derived from waste products of combustion, directing such air to the burner through which the furnace is being fired while stopping flow of air to the other burner, periodically reversing the firing from one burner to the other, and maintaining flow of air through the preheating equipment during these changeovers while flow of air to both burners is stopped.

3. A method of introducing air alternately to an opposed pair of burners in a reversing type furnace comprising preheating compressed air with heat derived from waste products of combustion from the furnace, the air temperature being near the maximum the preheating equipment is capable of withstanding, directing such air to the burner through which the furnace is being fired, while stopping flow of air to the other burner, periodically reversing the firing from one burner to the other, and maintaining flow of air through the preheating equipment during changeovers to avoid overheating of this equipment while flow of air to both burners is stopped.

4. A method of atomizing liquid fuel in reversible open hearth furnaces comprising preheating compressed air, applying such air as atomizing fluid to a burner through which the furnace is being fired while stopping flow of air to the other burner, and maintaining flow of air through the preheating means during changeovers in firing from one burner to another while flow of air to both burners is stopped.

5. A method of atomizing liquid fuel in reversible open hearth furnaces comprising preheating compressed air with heat derived from waste products of combustion, applying such air as atomizing fluid to a burner through which the furnace is being fired while stopping flow of air to the other burner, periodically reversing the firing from one burner to another, and maintaining flow of air through the preheating means during these changeovers while flow of air to both burners is stopped. V

6. A method of atomizing liquid fuel in reversible open hearth furnaces comprising preheating compressed air with heat derived fiom waste products of combustion of the furnace, the air temperature being near the maximum the heating device is capable of withstanding, applying such air as the atomizing fluid to a burner through which the furnace is being fired while stopping flow of air to the other burner, periodically reversing the firing from one burner to another, and maintaining flow of air through the heating device during these changeovers to avoid overheating the heating device while flow of air to both burners is stopped.

References Cited in the file of this patent UNITED STATES PATENTS 731,300 Holland June 16, 1903 820,210 Koons May 8, 1906 FOREIGN PATENTS 374,514 Great Britain June 13, 1932 France June 3, 1940 

1. A METHOD OF INTRODUCING AIR ALTERNATELY TO AN OPPOSED PAIR OF BURNERS IN A REVERSING TYPE FURNACE COMPRISING PREHEATED COMPRESSED AIR, DIRECTING SUCH AIR TO THE BURNER THROUGH WHICH THE FURNACE IS BEING FIRED WHILE STOPPING FLOW OF AIR TO THE OTHER BURNER AND MAINTAINING AIR FLOW THROUGH THE PREHEATING EQUIPMENT DURING CHANGEOVERS TO THE OTHER BURNER WHILE FLOW OF AIR TO BOTH BURNERS IS STOPPED. 